What happens if — or when — Mark Carney and the Liberals get to a majority?

If or when Prime Minister Mark Carney's Liberals succeed in cobbling together a majority in the House of Commons, it will surely be one of the most unique majorities in Canadian political history — cobbled together from 166 MPs elected as Liberals last spring, at least four floor-crossers and perhaps two or three byelection victories.

Those four party-switchers are remarkable enough. But they have now come from two different parties — the Conservatives and the NDP — that are, for the most part, diametrically opposed. Until today, it might have been hard to imagine that Matt Jeneroux, elected four times as a Conservative in Edmonton, and Lori Idlout, elected twice as the NDP MP for Nunavut, could sit in the same party caucus. 

At the very least, the narrative that Carney was governing like a Progressive Conservative is somewhat more complicated now.

Pending any further floor-crossings — and at this point it would seem foolish to assume there won't be more — the extent of a Liberal majority now hinges on the fate of three byelections, two of which the Liberals are widely expected to win.

Victories in University-Rosedale and Scarborough Southwest — two Toronto ridings the Liberals won comfortably less than a year ago — would bring the Liberals to 172 seats. At that point, the government could have some assurance of its ability to at least survive any confidence votes in the House.

A win in Terrebonne — where a rare judicial annulment has necessitated a byelection — would bring the Liberals to 173 seats. At that point, the Liberals could gain a majority on House committees and have a freer hand to advance legislation without having to negotiate compromises with the opposition.

The potential ramifications of Idlout's move are thus not small. But they also extend in several different directions.

For the NDP, a party already brought to a historic low by last year's election, this is yet another blow.

Fifteen years ago, the NDP won 103 seats in what seemed to be an electoral breakthrough for the traditionally third-place party. Its next leader — who is set to be chosen at the end of the month — will inherit a caucus of six MPs, at most. If Alexandre Boulerice follows through on a move to provincial politics in Quebec, the NDP will be down to five MPs.

For the Conservatives, Idlout's move was another chance to restate their argument that something underhanded is afoot.

"Mark Carney is using backroom deals to seize a costly majority that voters rejected," Conservative Leader Pierre Poilievre argued in a social media post.

Whether there is a wrong way to gain a majority in the House of Commons is a philosophical question that can be debated endlessly. But if, as opinion polls suggest, the Liberals have opened up a sizable lead over the Conservatives, the Conservatives might not actually mind being assured that the next federal election won't happen anytime soon.

Of late, Poilievre's Conservatives have seemed keen to be seen working constructively with the Liberals. But in the context of a hung Parliament — where no party has a majority — such collaboration can be necessary, at least so long as one wishes to avoid an election. In a majority situation, an opposition party is much more free to oppose without consequences.

So if the math changes, will the Conservative opposition's demeanour also change?